Dioxovanadium(V) complexes with N,N,O-donor monoanionic ligands: Synthesis, structure and properties

Abstract

Dioxovanadium(V) complexes having the general formula [VO2(phsalR)] have been synthesized in 52-63% yields by reacting one mole equivalent each of VOSO4 · 5H2O, 4-R-2-(pyridin-2-yl-hydrazonomethyl)-phenols (HphsalR, where R = H, OCH3, Cl, Br and NO2) and N(C2H5)3 in water-acetonitrile (1:1.3) mixture. The complexes have been characterized by elemental analysis, magnetic susceptibility and spectroscopic (IR, UV-Vis, NMR and EPR) measurements. The physical properties of the complexes are consistent with the +5 oxidation state of the metal ion in them. The X-ray structure of a representative complex, [VO2(phsal)] (R = H) has been determined. The metal centre in [VO2(phsal)] is in square-pyramidal N2O3 coordination sphere. The monoanionic pyridine-N, imine-N and phenolate-O donor phsal- and one of the two oxo groups form the N,N,O,O basal plane and the other oxo group satisfies the fifth apical coordination site. This square-pyramidal molecules form weakly associated dimeric units due to the participation of the oxo group at the basal plane in the V-O-V bridge formation. The structure of [VO2(phsal)]2 can be described as two edge-shared VN2O4 octahedra. In the crystal lattice, these dimeric units form infinite one-dimensional chain structure via intermolecular N-H⋯O{double bond, long}V hydrogen bonding interaction. © 2006 Elsevier Ltd. All rights reserved.